含横向裂纹悬臂梁的损伤检测

研究了含有横向裂纹的悬臂梁的弯曲问题,并给出了一种对悬臂梁进行损伤检测的方法.将梁的损伤模拟为一个附加柔度,根据理论分析,建立了梁的挠度和损伤位置以及附加柔度之间的关系,定义损伤处梁的剖面惯性矩与完整剖面的惯性矩之比为惯性矩系数,结合有限元法,建立附加柔度和惯性矩系数的关系,给出了一个由附加柔度计算惯性矩系数的公式,根据惯性矩系数估计损伤程度.通过一个梯形截面梁的算例证明,提出的计算公式和损伤检测法是准确有效的.     

Cytolytic and K+ channel blocking activities of β-KTx and scorpine-like peptides purified from scorpion venoms

Among the scorpion venom components whose function are poorly known or even show contrasting pharmacological results are those called “orphan peptides”. The most widely distributed are named β-KTx or scorpine-like peptides. They contain three disulfide bridges with two recognizable domains: a freely moving N-terminal amino acid sequence and a tightly folded C-terminal region with a cysteine-stabilized α/β (CS-αβ) motif. Four such peptides and three cloned genes are reported here. They were assayed for their cytolytic, antimicrobial and K ⁺ channel-blocking activities. Two main characteristics were found: the existence of an unusual structural and functional diversity, whereby the full-length peptide can lyse cells or kill microorganisms, and a C-terminal domain containing the CS-αβ motif that can block K ⁺ channels. Furthermore, sequence analyses and phylogenetic reconstructions are used to discuss the evolution of this type of peptide and to highlight the versatility of the CS-αβ structures. Received 13 August 2007; received after revision 30 October 2007; accepted 2 November 2007     

基于IPv6的下一代网络在校园网中的实现

本文简要介绍了下一代互联网的发展,研究了从IPv4到IPv6的过渡方式,包括双协议栈技术、隧道技术以及网络地址转换／协议转换技术;重点解决了以下几个问题：①通过在校园网出口增加双栈交换路由设备并使用双栈技术,实现了一条线路同时连接CERNET-9CERNET2网络;②在校内核心交换机上建立ISATAP隧道入口,使校内用户可以通过隧道方式访问CERNET2资源;③在UNIX系统上使用Bind9搭建了基于IPv6协议的域名系统,能同时为IPv4和IPv6网络解析校内IPv6域名。目前,重庆师范大学IPv6网络的基础结构和基础应用服务已经构建完毕,为以后从IPv4网络向IPv6网络过渡做准备,也为没有构建IPv6校园网的学校提供参考。     

端面磨损对U型槽动压机械密封性能的影响

以核主泵所用U型槽动压密封环为对象,研究了密封端面因介质中微粒所引起的磨损问题.结果表明：端面动压槽根部产生的初期磨损将造成刚度和泄漏率增加,且随着磨痕数量的增加,泄漏率呈线性增加;当磨痕贯穿密封坝而使U型槽根部与端面低压侧短路时,将会造成泄漏率的阶跃上升和刚度急剧下降.在实际使用的过程中,多个U型槽将会同时出现磨痕,当一处磨痕贯穿密封坝时,将造成大量介质泄漏,且磨痕越深,其泄漏率越大,最终导致密封失效.     

模糊随机需求条件下三级供应链的数量折扣协调策略

为了分析模糊随机需求条件下三级供应链协调策略,考虑提前期内需求为模糊随机变量, 建立由供应商、制造商和零售商所组成的三级供应链优化决策和数量折扣协调模型, 其中订单量、再订货点为决策变量.首先推导出提前期内需求为模糊随机变量条件下的各成员成本和供应链总成本函数,然后设计相应的算法对模型进行求解,最后通过算例验证了模型的实用性, 并进行比较分析.结果表明：采用数量折扣协调策略能够降低三级供应链总成本;如果在制造商的上下游企业同时引入数量折扣策略,此时所引起的三级供应链总成本低于仅在制造商的下游企业引入数量折扣时的三级供应链总成本,亦低于未提供任何数量折扣策略时的三级供应链总成本;模糊随机需求条件下三级供应链总成本高于随机需求条件下的三级供应链总成本.     

应用型本科高校计算机类专业学生创新实践能力的培养——基于“恩智浦”杯智能车竞赛

针对应用型本科高校计算机类专业学生创新实践能力的培养，提出了一种以全国大学生“恩智浦”杯智能车竞赛为载体，分4个阶段逐步培养学生创新能力的培养体系。经过9 a多的努力，形成了良好的培养流程，学生获得优秀竞赛成绩、对口就业率提高。     

Reconstructing Native American population history

The peopling of the Americas has been the subject of extensive genetic, archaeological and linguistic research; however, central questions remain unresolved. One contentious issue is whether the settlement occurred by means of a single migration or multiple streams of migration from Siberia. The pattern of dispersals within the Americas is also poorly understood. To address these questions at a higher resolution than was previously possible, we assembled data from 52 Native American and 17 Siberian groups genotyped at 364,470 single nucleotide polymorphisms. Here we show that Native Americans descend from at least three streams of Asian gene flow. Most descend entirely from a single ancestral population that we call 'First American'. However, speakers of Eskimo-Aleut languages from the Arctic inherit almost half their ancestry from a second stream of Asian gene flow, and the Na-Dene-speaking Chipewyan from Canada inherit roughly one-tenth of their ancestry from a third stream. We show that the initial peopling followed a southward expansion facilitated by the coast, with sequential population splits and little gene flow after divergence, especially in South America. A major exception is in Chibchan speakers on both sides of the Panama isthmus, who have ancestry from both North and South America.     

Preface

正All-optical implementations of signal processing have attracted a great deal of attention due to the unique potential of this approach to overcome the bandwidth and speed bottleneck of electronic devices.Many all-optical signal processing techniques,offering processing bandwidths up to several THz,have been proposed and successfully employed in a wide range of areas,such as     

基于丝网印刷技术的电化学酶联免疫吸附

为研究基于丝网印刷技术的电化学酶联免疫吸附(ELISA)的效果,在塑料基板上印刷96孔电极单元,形成标准96孔ELISA检测板,建立电化学检测与ELISA实验的关联,检测板每孔底部为独立电化学单元,由碳电极、对电极和银参比电极组成,形成双面印刷基板,基板通过96×3针式镀金特定连接器连接至恒电位仪。结果表明,96孔三电极电化学丝网印刷电化学阵列作为ELISA检测是可行的,多通道恒电位仪可同时测量8个孔数据。     

用混合遗传算法求解物流配送路径优化问题

为了改善物流配送路径优化问题的运算质量,提出一种将遗传算法和模拟退火算法相结合的混合遗传算法。通过仿真 实例验证,证明混合遗传算法的解优于单纯使用遗传算法和模拟退火算法所得到的解,同时混合遗传算法与传统优化算法相 比收敛速度更快,分配结果更优良,具有很好的应用价值。